A Lidl spokeswoman said: “2013 has seen our best performance to date over the Christmas period. Our upper-middle-class and middle-class customers now make up 24 per cent of all our shoppers.”

Lidl plans to open up to 20 new stores in 2014, along with a distribution centre in Northfleet, creating up to 2,000 jobs. It currently has 600 UK stores.

A spokesman for rival Aldi said: “We had our busiest Christmas since opening in the UK, record numbers visited Aldi.”

The chain, which has about 500 stores, is set to unveil its Christmas trading figures next week. It plans to open 50 new stores and create 6,000 jobs in the year to September.

Rahul Sharma, retail analyst at Neev Capital, said: “It is looking like a double-digit Christmas for both Aldi and Lidl. The quality has improved so it is no surprise that a broader range of people are shopping there now.”

Aldi plans on opening 50 new stores in the UK [GETTY]

Our research saw Aldi and Lidl poised to scoop festive foodshop business

Meanwhile Sainsbury’s is expected to report its first negative numbers for 35 quarters this week. Tesco’s festive trading is also set to be slightly down.

Marks & Spencer, which will announce results for its third quarter this week, is expected to have had mixed success.

Clive Black, analyst at Shore Capital, said: “We would expect M&S and Waitrose, among the premium supermarkets, to have gained market share with positive like-for-like sales. But M&S Food is likely to be in stark contrast to its general merchandising division.”

Major stores are looking to win back customers with heavy discounting. Last week Sainsbury’s launched its “biggest ever” January sale and the Co-op, which is also expected to have suffered over the festive period, said it would offer customers up to 25 per cent off a future shop.

Black added: “We expect a brighter year for the supermarkets and we do not believe that Aldi and Lidl will have quite such a free run. We also expect the Big Four, Tesco, Asda, Sainsbury’s and Morrisons, to start fighting harder.”